Inductive proximity sensors are well known in the art and usually comprise a coil that is wound around a ferrite core to form an oscillator. The inductive proximity sensor is connected to a circuit board which is equipped with integrated circuits, for instance an electronic analyzing unit and an amplifying circuit. When a metallic object approaches the sensor, the oscillator is detuned and thus a signal in response to the approaching object is generated. All components of the sensor are integrated within an elongated housing. The sensor coil is arranged at a front end of the sensor and a peripheral contact element for connecting the sensor to external electronic components, such as a plug connector or an electrical lead, is arranged at the opposing back end of the sensor. A circuit carrier, usually a printed circuit board (PCB), carries the sensor electronics and is electrically connected to the peripheral contact element.
There exist different concepts in the prior art for equipping sensors using a plug connector as the peripheral contact element. A conventional plug connector can be screwed or pressed into the housing and then connected to the PCB by manually soldered electrically conductive leads. Alternatively, a flexible printed circuit board can be soldered directly to the plug connector. In a further alternative, a conventional plug connector can be assembled with a cable and an edge connector which is connected to the PCB; this variant, however, requires considerable space. It is further known to directly assemble the plug connector on the PCB and mount the PCB with the plug connector in the housing such that the plug connector remains accessible via a suitable opening in the housing. According to a further conventional arrangement, a plurality of contact pins are assembled individually on the PCB and allowed to extend to the outside through a respective support structure in the housing. Finally, it is known to overmold a plug connector at the housing and contact the PCB using a lead frame which is pressed-in or soldered to the PCB.
Some applications of inductive proximity sensors require that the sensor is equipped with a cable of a suitable length as the peripheral contact element instead of a plug connector. Such a cable can be soldered manually to the printed circuit board. Alternatively, the cable can be provided with an edge connector. Conventional cable connections achieve a sealed encapsulation of the sensor components as well as the necessary strain relief by providing an additional overmolding step. Alternatively, a cable gland is often used for providing sealing and strain relief.
Inductive proximity sensors are fabricated in mass production and therefore the assembly of the proximity sensor must be simple and cost-efficient; it is most simple and cost-efficient to require the choice of a particular peripheral contact element as late as possible in the fabrication process and to avoid manual soldering.